In conventional film/screen radiography, an x-ray image is formed on film by exposing an object (such as a patient body part) to a source of x-rays.
The developed film is then used by a physician for diagnostic purposes. In order to facilitate computer processing of an x-ray image on film, the film is digitally scanned to produce a digital x-ray image. The digital image can be processed, stored, transmitted to remote locations and displayed on a video monitor. One type of digital film scanner uses a laser to produce a laser beam which is scanned in a line across an information medium, such as radiographic film, as the medium is translated in a direction perpendicular to the line scan direction. Light transmitted or reflected from the film is collected and converted to an electrical image signal by a photodetector.
Laser film scanners are disclosed in U.S. Pat. No. 4,818,861, issued Apr. 4, 1989, inventors Horiuche et. al. and U.S. Pat. No. 4,568,984, issued Feb. 4, 1986, inventors Juergensen et. al. The latter patent discloses the use of a cylindrical diffuse light collector located below a horizontally translated film which is scanned with a laser beam. The collector has a slot for receiving transmitted light into the collector cavity where the light is diffusely reflected to a photodetector. Such a collector is disadvantageous since dirt can enter the collector cavity through the light collecting slot. Gravity pulls dirt onto the surface area of the cavity which the laser beam first strikes after passing through the film. Large particles of dirt will result in a streak artifact in the image if the dirt reflectivity is different than the diffusely reflective surface of the collector cavity.
U.S Pat. No. 2,821,103, issued Jan. 28, 1958, inventor B. C. F. Blet; U.S. Pat. No. 3,327,583, issued Jun. 27, 1967, inventors G. F. Vanderschmidt et. al.; U.S. Pat. No. 3,648,056, issued Mar. 7, 1972, inventors T. B. Buttweiller et. al.; U.S. Pat. No. 4,868,383, issued Sept. 19, 1989, inventor A. F. Kurtz et. al., disclose various configurations of light integrating assemblies which do not solve these problems.
It is thus desirable that such streak artifacts be eliminated. It is also desirable that the light collector have high light collection efficiency, be easy and economical to manufacture and be configured so that photodetectors are shaded from scattered transmitted light.